I am not familiar with modern brushless motors, but we looked into AC boost pumps with a built in inverter at Cessna. They cost quite a bit more and reliability is highly dependent on the quality of the inverter, as well as its power supply. We had a bad earlier experince with this on the A/T-37 IIRC. Main bearings on wet motor boost pumps are not significant wear items.

That's not how it works. They are a sonic nozzles, so more or less once the pressure differential across the nozzle gets high enough a shockwave forms and the mass flow becomes constant. In the Malibu that's around 25" MAP. Above that MAP no additional bleed is taken from the motor. Below 25" the outflow valve does have to move with any power changes but it will keep it fully pressurized down to about 20".

Like Chuck said no real performance lost due to the bleed air. My newly OH'd TSIO550C's critical altitude is 21,900, I doubt a TTx driver does any better with the same motor.

I could see a potential case for electric pressurization on a piston powered aircraft.

My Columbia 400 is unpressurized, but it gets cabin heat from the turbocharger discharge air. It is plumbed similarly to pressurization systems, where air is taken via sonic venturi nozzles from each of the two turbos. That air is heated by the compression of the turbo, then fed directly into the cabin's environmental controls.

I will say, that the heat can be kind of anemic at times and certain operating conditions. There's an STC for a heating system that a heater muffler around the crossover tube to improve cabin heat.

I'd be curious how much power is required to maintain cabin pressure in a small airplane - because I don't know. It seems within the range of a turbocharger, so it isn't unpossible.

It could keep cabin pressurization separate from engine operation, perhaps offering other efficiencies.

Yep, I was typing on my phone from memory while enjoying a beverage after work, and I was trying to avoid absolutes. Clearly I failed ...

Form the quoted site:


So let me say density is relatively constant as the pressure increases (PV=nRT), so does the temperature, so thus mass flow is relatively constant through the sonic nozzle... I was trying not to type in absolutes as nothing in real life follows the ideal gas laws.

Experimentally, this can be seen by making relatively rapid changes in manifold pressure above the choked flow position and noting it has an imperceivable impact on cabin pressure/altitude. Below the chocked flow position (~25" on my plane) the response of the outflow valve becomes a factor and can be seen/felt by a temporary rise in cabin pressure when I pull power out, or a temporary reduction in cabin pressure if I apply power. It'll eventually settle back to the set value as long as the outflow valve doesn't fully close, but power changes below that choked flow does have a noticeable impact on the cabin altitude.

Anyway back on topic...

Sorry, what is the actual topic now?

We need to remember the basic rule to get investors is to make it as unusual as possible. Humans have the bias that if looks like what is already built it can't be an improvement.

a good example is Ecomotors which is a strange redesign of an opposed piston design. they got over $50,000,000 without one running as I remember. I think they got 25 million from Gates as I remember

so if you want to get investors make it as strange as possible using some fancy new mathematics etc.

From what I've seen, investors are not very good an evaluating risk beyond low / high. One something is "high" risk there seems to be little distinction between 20% chance of success and .000000001% chance.

I've been paying a lot of attention to the nuclear fusion industry as part of my job, and I see huge investments in ideas that have microscopic chances of success - on the idea that it would be "really great if it worked".

Well, success is only a decade away (been there for 50 years).

AI guesses 20 cfm required per person at 25,000 ft and the power required for a 6 person plane to be 3 hp drawn from the alternator.
Inlet air at -20°C into the compressor would exit the compressor at 36°C, per AI.

That's about 80A for a 28V system- quite a lot more than a parasite load though still something you can realistically design around. Multiply that by an appropriate safety factor to not only cope with normal wear and tear, but also a moderate leak lasting several minutes (i.e. time to descend from cruise to 10,000').

Other than sizing the air pump appropriately, consider the electrical budget and systems architecture, like what are the other electrical "pigs" (i.e. electric anti-ice, lights, flaps, landing gear).

Landing lights, flaps and landing gear all draw power at low altitude, not at pressurization altitudes.

Landing lights, flaps and landing gear all draw power at low altitude, not at pressurization altitudes.

I don't think the number of people onboard would have any effect on the airflow required beyond meeting their oxygen requirements. If that's what's driving the airflow requirement I think it would be more like 1 cfm per person since that would provide 5 lpm of O2. Other than that I think the cfm needed would mostly be a function of how big the leaks are.

Are we talking exclusively about piston aircraft? I still do not understand how you deal with environmental needs, since the ACM provides the heat necessary at high altitudes. Where is your heat going to come from? I do love the idea of electric pressurization, but it would seem to create other issues.
On the 441 for example, the ACM also provides air conditioning, and does so very effectively. You would need an engine driven or electric compressor in this instance to provide cooling.